1. Technical Field
The subject matter described here generally relates to electricity measuring and testing, and, more particularly, to conductor identification or location including phase identification.
2. Related Art
As illustrated in FIG. 1, electric power distribution networks 2 are used by the electric utilities to deliver electricity from generating plants 4 to end-users, such as consumers or customers 6. Although the actual distribution voltages will vary from utility to utility, in the non-limiting example illustrated here, three-phase power from a generating plant 4 is fed to a generator step up transformer 8 which provides 765 V to 138 kV power to transmission lines 10. High voltage power from the transmission lines 10 is delivered to various substations 12 at which other transformers 8 step this voltage down to lower three-phase voltages and ultimately separate the power into three single-phase feeder lines 14. Each of these feeder lines 14 then branch into multiple circuits to power a plurality of local pole-mounted or pad-mounted transformers 8 which step the voltage down to final voltages of 120 and 240 volts for delivery and metering at commercial and residential customer locations 6.
So called “smart meters” 16 monitor the electrical consumption by consumers 6 in detail and then communicate that information back to the utility in a process referred to as “telemetering.” For example, the General Electric Company offers a family of “kV2c” meters and accessories. Various telemetering networks have been proposed for these and other electrical smart meters 16, including cell/pager networks, licensed and unlicensed radio networks, and power line communication networks. For the power line telemetering network illustrated in FIG. 1, it is important to know which phase the smart meter is connected and that this information is transmittable through the transformers 8.
Ideally, the feeder circuits 14 are designed such that the loads on each single-phase output of any three-phase transformer 8 are equal. However, as new customers are added over time, any one of the phases may become more heavily loaded than the others. In order to re-balance that loading, some of the branch circuits 14 may then be switched from the more heavily loaded phase to the more lightly loaded phases.
Consequently, the records telling a smart meter 16 installer which phase an individual customer 6 is on are incomplete or inaccurate. Therefore, in order to accurately identify the current phase of a particular feeder branch, utility company personnel must physically trace a cable run back through various distribution facilities until they reach a point in the distribution network 2 at which the phase is definitively known. This can be a very time-consuming and labor intensive process which can often lead to incorrect information. During storms or emergencies this can also lead to safety issues as well.